1. Field of the Invention
The present invention relates to a color image processing apparatus for processing color images.
2. Description of the Prior Art
As an example of a color printer, a color ink jet printer is composed as shown in FIG. 1, wherein first to fourth nozzle heads 2-1-2-4 arranged from right to left respectively emit cyan (C), magenta (M), yellow (Y) and black (K) colored inks supplied respectively from ink reservoirs 4 through flexible tubes 3, and driving signals to said nozzle heads are supplied by plural wires in flexible cables 4-1-4-4, a terminal plate 5 and a combined flexible cable 6. A carriage 1 of the above-described structure is supported by two rails 7 and is put into reciprocating motion to perform main scanning in a direction X by an endless belt 8 driven by a stepping motor 9, while a recording sheet 11 extended between paired rollers 12, 13 is advanced in a direction Y to perform subsidiary scanning by a stepping motor 14 linked to the paired rollers 13, whereby a color image is recorded on said recording sheet 11 by colored inks emitted from the nozzle heads 2-1-2-4. The range of the main scanning is limited by stoppers 10-1, 10-2 positioned on both ends of the reciprocating path of the carriage 1. A sensor 15 is provided on the carriage 1 to detect the image recorded by the nozzle heads 2-1-2-4, while another sensor 16 is provided in a position distant in the feeding direction of the recording sheet 11 by the paired rollers 13 to detect the recorded image in the direction of subsidiary scanning.
In the ink jet printer of such structure, with the nozzle heads 2-1-2-4 arranged in the order of cyan (C), magenta (M), yellow (Y) and black (K) colors on the carriage 1, the order of color ink dots superposed on the recording sheet 11 when the carriage runs to the right is opposite to that when the carriage runs to the left, as will be apparent from the comparison of the subdivisions A, B, C and D in Fig. 2. In order to record a color image with intermediate tones, inks of complementary colors of cyan (C), magenta (M) and yellow (Y) respectively corresponding to red (R), green (G) and blue (B) are employed and superposed to achieve subtractive mixing necessary for reproducing intermediate tones. Also each ink does not represent genuine complementary color since the density change at the boundary of spectral region is not sharp. Consequently, in case the dots of inks of such complementary colors are deposited superposedly on the recording sheet 11, the mixing of colors varies according to the order of deposition of ink because the ink dot directly deposited on said recording sheet 11 does not expand due to sufficient absorption into the sheet while other ink dots show expansion due to insufficient absorption into the sheet, thus leading to different size relationships of the ink dots depending on the order of deposition, and also because the absorption and reflection of the incoming light are affected by the vertical order of the ink dots. In the conventional color ink jet printer, the intermediate color tone obtained by the main scanning motion of the ink nozzle heads becomes different in the forward motion and in the reverse motion due to the above-explained reasons, thus significantly deteriorating the quality of the recorded color image.